Chlorine Dioxide for Water Treatment

Chlorine dioxide is a heavy, reddish-yellow gas used as a bleach and disinfectant. It was discovered by Sir Humphrey Davy, a British chemist and inventor, in 1814. Chlorine dioxide was first used as a water treatment at a Belgian spa in the early 1900’s, and since then it has been known as a powerful disinfectant. Chlorine dioxide is preferred to mere chlorine disinfection, largely because of refined qualities that contribute to better-tasting water as well as its ability to eradicate harmful bacteria and viruses.

Major Benefits

Among the major benefits of chlorine dioxide, the most important to human health is its disinfectant abilities. This applies not only to basic microorganisms that permeate water at its source, but also to bacteria and viruses that travel through water and can infect humans and animals. Other benefits include controlling the taste and odor of water, as well as controlling iron, magnesium, hydrogen sulfide and phenolic compounds, all of which derive from water sources. Thus, chlorine dioxide offers a number of advantages for water purification and disinfection.

What Chlorine Dioxide Is and How It Works

Even though chlorine dioxide derives from chlorine, it does not disinfect primarily with chlorine. It uses the oxygen in its composition to disinfect. On the molecular level, it is relatively small but strong. This is because its atoms are excitable when introduced in higher concentrations. Dilution calms its reactive activity a bit. Store it away from sunlight, which can change its structure altogether.


Since it is a free radical in molecular form, chlorine dioxide retains its water-soluble nature only when chilled at less than 11 degrees F. When the temperature rises, it becomes a volatile and potentially dangerous gas. Chlorine dioxide is either manufactured on-site or transported with extra safety measures because of its instability–e.g., the chemical is contained in chilled, darkened canisters that have no access to a heat source.


Chlorine dioxide is generated by chemical reactions that include: acid-chlorite, aqueous chlorine-chlorite, recycled aqueous chlorine–aka “French loop”; gaseous chlorine-chlorite, electrochemical and acid/peroxide/chloride solutions. The process for generating chlorine dioxide depends on how it will be used and subsequently stored.


As a bactericide, chlorine dioxide kills E. coli, bacillus anthacoides, Eberth Ella typhosa, Shigella dysenteria, salmonella paratyphi B., pseudomonas aeruginosa, staphylus areous and other deadly bacteria. As a virucide, it deactivates poliomyelitis in a highly efficient manner. It also eradicates protozoa, which causes many illnesses. It eradicates many other viruses and bacteria, particularly those found in water.

Chlorine dioxide is a heavy